electrical efficiency

[flange]

so lets say youve got two machines, one twice as big as the other. say a five hundred and a 1000 tonner. without getting nutso about total plant energy use, etc , what is more efficient to run, one large machine at near full capacity, or both, with the smaller one loaded up, and the larger one partially loaded? nott freek drive machines or turbo core, just plain jane older yorkies. i know my opinion, just looking for others.

[CumulusMech]

so lets say youve got two machines, one twice as big as the other. say a five hundred and a 1000 tonner. without getting nutso about total plant energy use, etc , what is more efficient to run, one large machine at near full capacity, or both, with the smaller one loaded up, and the larger one partially loaded? nott freek drive machines or turbo core, just plain jane older yorkies. i know my opinion, just looking for others.

I put my money on running the 1000 tonner . What about you flange ?

[mallron]

Ok, from what I understand chillers separate the men from the boys using part-load efficiency (Centrifugal). So, I would think that most chillers are at their best when running fully loaded (rare, which is why people like Trane, because of part-load eff.) So, my educated guess to your question would be to run the biggun wide open.

[cperk]

check them in both situations check ampdraw and voltage I think you will find a watt is a watt is a watt or in this case a Kw is a Kw is a Kw we have a few chillers that dont have enough water flow running through a single chiller to supply the secondary loop so we have to run two

[jayguy]

...I think you will find a watt is a watt is a watt...

not exactly (uh oh...probably getting a little nutso)

while the exact wattage that you would pay for is the same, the power factor is lower in a lightly loaded machine. lower power factor COULD cause a higher power factor charge from the utility (individual results may vary)

also, your kW/ton drops as the chiller unloads.

[stanbyyourword]

thats a good point, while power cosumption may be lower unloaded , how many tons are your getting from the chiller vs pulldown and run times , in other words a more efficient chiller ie approach , balanced head pressures, in some cases its more efficient to cycle off , in others to run fully unloaded, all plants are different for sure. Im wondering some of you chiller techs , what percentage of thermal storage installations your are seeing going in lately?

[9675]

I say 1000 by itself too, but i am more intrested in how you would get 500 ton to run at 100% and 1000 ton at 1/2 capacity,assuming 1000 ton load, I have never seen it happen, have you!

[flange]

well, yes as a matter of fact i have. but it isnt exactly easy. it depends on plant configuration, controls, and so forth. at any rate, older machines without freek drives are clearly less efficient at part load. this is due to running the motor at a fixed speed say sixty htz, but closing inlet giude vanes for capacity control. motors are less efficient when running in certain parts of their horsepower curve, and it drops off as you go lower. so kw per ton goes up. running near full capacity should be the most efficient on this type of machine. throw in a drive and everything changes, but you all already know that. the question actually came to me from a client whom we do some work for, but not their chillers. the chiller service company was recommending that since it was a bizillion degrees here for the last few days, that starting the smaller machine around noon and loading it up all the way was a better solution to loading up the larger machine all the way. by the way, the3y also did not consider the penalty for the demand. effing jo's.